PARIS — Secretary of State John Kerry told the Syrian opposition that support for the group could be reduced if it decides not to attend the upcoming peace conference in Switzerland, Western officials said Tuesday.

Kerry and a team of senior US officials met Monday with Ahmad Assi al-Jarba, the president of the Syrian opposition coalition that the West is backing, and other opposition officials.

That rebel coalition has been concerned that its influence within Syria, which is already limited, would be undermined further if it participated in a drawn-out peace conference that did not lead to any results.